Bio-mask with integral sensors

ABSTRACT

A gas mask for use with associated monitoring and controlling apparatus is provided. A device for monitoring of patients with sleep disorders, breathing disorders or for anesthesia is provided. Different types of sensors on or in the mask and straps or caps connected to the mask include but are not limited to oximetery sensors, patient position sensors, eye movement sensors, leak detection sensors, EEG, EMG, EOG, ECG, PTT, microphones, pulse, blood pressure, oxygen saturation, temperature, movement sensors, position sensors, light sensors, leak detection sensors and gas delivery sensors. Another application provides for gas delivery to a bio-mask controlled, in part, via communication from a pacemaker to a bio-mask controller.

RELATED APPLICATIONS

[0001] This application is a continuation-in-part of U.S. Ser. No.09/465,054, filed Dec. 16, 1999, and incorporated herein in itsentirety.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to a breathing mask with built in sensorsfor monitoring patients with sleep apnea, breathing disorders for useduring anesthesia or ventilation support.

[0004] 2. Description of the Related Art

[0005] Masks such as shown in U.S. Pat. No. 5,243,971 for applying apositive pressure to patients with apnea and other breathing disordershave been developed. These masks provide seals for preventing air fromescaping from the mask at the junction of the mask and face. Other typesof masks for gas delivery to a patient are also in common use.

[0006] Measuring air flows to a patient has been accomplished bymetering sensors in the air supply connected to the mask as in U.S. Pat.No. 5,503,146 or by belts around the patients chest to measure hisbreathing as in U.S. Pat. No. 5,131,399.

[0007] Some devices such as in U.S. Pat. No. 5,507,716 provide sensorscombined with sleep masks for covering the eyes of a patient. Howeverthere is no known example of sensors built into breathing masks formonitoring or studying patients with breathing disorders.

[0008] Currently if a patient is to be carefully monitored a pluralityof electrodes or sensors would have to be individually applied to thepatient and wired to recording equipment. The plurality of sensors andtangle of ensuing wires impede the usage of such monitoring equipment.Sensors providing useful information include Electro-encephalogram(EEG), electromyography (EMG), electro-oculogram (EOG),electro-cardiogram (ECG), Pulse Transit Time (PTT), gas flow sensors,temperature sensors, microphones, blood oxygen meters, blood pressuresensors, pulse sensors, patient movement, position, light, activitysensors, mask leakage, mask pressure, eye movement by polyvinylideneflouride-(PVD) or Piezo, and other means of gathering data about thepatient or his environment.

[0009] It is very inconvenient for the patient and the health careworker to attach a series of different devices to a patient to monitor aplurality of different parameters simultaneously. Therefore a singledevice for easily measuring a plurality of parameters is desired.

SUMMARY OF THE INVENTION

[0010] The invention relates to providing sensors in breathing masks tomake it easy to monitor a patient. The mask has a soft pliable sealmaterial around its perimeter in contact with the patient's face to forma secure seal therewith. Sensors may be recessed into the soft pliableseal material at the surface for contact with the skin of the user whenthe mask is applied to the user's face. The wiring for the sensors maybe inside the soft pliable seal material insulating the wires fromdamage during use of the mask. Many sensors can be incorporated into themask. Sensors may be placed on the perimeter or on other portions of themask not in contact with the skin. Sensors may also be placed on strapsor caps used in conjunction with the masks or on other devices used withthe mask.

[0011] Monitoring of patients with sleep disorders, breathing disordersor for anesthesia is made easier and more convenient for the patient andfor the health care provider since all the sensors needed are built intoa mask which is easily and quickly placed on the patient with all thewiring to the sensors integral with the mask and accessed by a singleplug.

[0012] The types of sensors on or in the mask and straps or capsconnected to the mask include but are not limited to oximetery sensors,patient position sensors, eye movement sensors, leak detection sensors,EEG, EMG, EOG, ECG, PTT, microphones, pulse, blood pressure, oxygensaturation, temperature, movement sensors, position sensors, lightsensors, leak detection sensors and gas delivery sensors.

[0013] Connections to outside sources of gases delivered to the mask areby a gas nozzle hook up on the mask. A connection to electrical powerand data output cables are by a plug in to a cable connecting to themask. Alternatively batteries in the mask and telemetry equipment in themask can provide power and transmission of the data to a microprocessoror computer. For portability the microprocessor can be attached to themask or be carried by the patient. Similarly a bottle of gas may beconnected to the mask and carried by the patient to allow mobility ofthe patient while wearing the mask.

[0014] Unique applications for the bio-mask include the capability toapply anesthesia-depth monitoring while administering anesthesia gas toa subject. The ability to monitor the patient non-invasively with thebio-mask while at the same time administering the anesthesia gas to thepatient provides a bio-feedback function for immediate and responsiveanesthesia depth of the subject. The bio-mask can be used to determinethe subject's sleep state by applying standard sleep staging criteria,such as that of R&K rules and/or the application of diagnostictechniques which analyze a number of EEG signals, such as BispectralAnalysis. The invention is unique in its capability to apply suchanalysis with the minimal-invasive application of a subject breathingmask.

[0015] R&K rules refer to “A Manual of Standardized Terminology,Techniques and Scoring System for Sleep Stages of Human Subject” byRechtschaffen and Anthony Kales, Editors 1968 which is hereby made apart hereof and incorporated herein by reference.

[0016] Another unique application for the bio-mask includes thecombination of the bio-mask with a cardiac pacemaker. It is envisionedthat the gas delivery to the bio-mask may be controlled, in part, viacommunication from a pacemaker to a bio-mask controller.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 shows a schematic view of the zones for sensors on theinside surface of a soft pliable material on the perimeter of thebreathing mask.

[0018]FIG. 2 shows a view of the sensors and wiring inside the softpliable material on the perimeter of the breathing mask.

[0019]FIG. 3 shows a side schematic view of the sensors and the wiringinside of the soft pliable material on the perimeter of the breathingmask.

[0020]FIG. 4 shows a side schematic view of the straps connected to themask with sensors embedded in the straps and the mask.

[0021]FIG. 5 shows a schematic view of the sensor zones on the perimeterof the breathing mask.

[0022]FIG. 6 shows a schematic view of the sensors on the inside surfaceof a breathing mask.

[0023]FIG. 7 shows a side schematic view of the mask with sensors on thesurface of the mask.

[0024]FIG. 7 shows a side schematic view of the mask with sensors on thesurface of the mask.

[0025]FIG. 8 shows a front elevated view of one embodiment of thesubject invention.

[0026]FIG. 9 shows a rear elevated view of the embodiment of FIG. 8.

[0027]FIG. 10 shows a side elevated view of the embodiment of FIG. 8.

[0028]FIG. 11 shows an exploded view of one embodiment of the subjectinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029]FIG. 1 shows the inside of mask 10 including the perimeter surface12 which contacts the patient's face. The perimeter surface 12 has aplurality of zones 20. Each zone 20 having a sensor 25 in a recess 29for measuring a parameter of the patient to be monitored or other datasuch as gas leakage. Other sensors 26 are on the mask 10 but not incontact with the patient's skin. These sensors 26 measure patient dataor related data such as ambient light, gas pressure in the mask orambient temperature.

[0030] The mask 10 has a gas connector 14 for connecting a hose 32 toprovide a gas to the mask 10 and a mask interface connector 16 forplugging in a cable 30 for a power supply and for data transmission

[0031] In some embodiments of the invention the sensors 25 do notrequire an outside source of power as the sensors such as heat sensorsand light sensors generate current.

[0032] The mask perimeter surface 12 is preferably made out of a softpliable material such as silicone rubber for making a good sealingcontact with the face of the patient to prevent gas leakage. Thematerial should be soft and pliable enough to follow the contours of theface. The perimeter surface preferably has recesses 29 on the surfacefor the insertion of sensors 25 so that the sensors can make contactwith the patient's skin when the mask is pressed against the patient'sface.

[0033] As seen in FIG. 3 a sensor or electrode 25 attachment to the mask10 preferably utilizes a rubber compound 28 such as silicon or othermedical grade type rubber embedded with carbon or other conductivematerials for electrical contact of skin to the mask. As shown in FIG. 2the recesses 29 are large enough to accommodate electrical connectionsto leads 27 which are buried in the soft pliable material under theperimeter surface 12. The leads 27 are thus protected from damage andelectrically insulated. Preferably the sensors 25 will plug into theleads 27 or printed circuits in the recesses 29. The leads 27 arepreferably on printed circuits embedded in the mask or fine wiresembedded in the mask and connect the sensors 25 to the mask interfaceconnector 16.

[0034]FIG. 5 shows conductive material 40 on the surface in zones 20,such as carbon embedded silicon, can be used on the surface of theperimeter 12 of mask 10 in separate zones 20 to conduct the electricalsurface energy from the patient's face. The conductive material 40 ispreferably moisture activated to improve electrical conductivity when incontact with the skin. The conductive material 40 may be utilized forsome or all electrode 25 contacts in the zones. Alternatively electrodes25 may directly contact the patient's face. The electrodes may also beinside of the soft pliable material on the perimeter 12 of the mask 10.

[0035]FIG. 4 shows a side view of the mask 10 and straps 35 used to keepthe mask in place on a patient. The straps 35 have sensors 25 connectedto leads 27, which connect the sensors to the mask interface connector16 and to cable 30 for transmitting data to a computer or other device.The sensors 25 in the straps 35 may be electro-encephalogram EEG sensorsfor measuring brain waves. The straps 35 may be replaced with a caphaving sensors therein. Alternatively a chin strap 37 may be used havingsensors 25.

[0036]FIG. 5 shows an example of the types of sensors 25 used in zones20 around the perimeter of the mask 10. Physiological signals from apatient's skin potential are detected by sensors in the zones 20 aroundperimeter 12 of mask 10. Conductive electrode paste 40 may be used toimprove the electrical contact between the sensors 25 and the surface ofthe skin. The conductive paste 40 can assist in reducing the impedancebetween the face and the electrical output from the sensors 25 in zones20. The conductive paste 40 may also assist in preventing gas leaks.

[0037] As an example of a mask sensor layout the following sensors andtheir functions are described. However many other types of sensors andarrangements of the sensors are possible.

[0038] Zone 50 is an electro-oculogram (EOG) to obtain electrical eyemovement reference signals from over the bridge of the nose.

[0039] Zone 51 is an EOG to detect electrical eye movement signals forthe inner left eye and zone 61 is designated for electrical eye movementsignals for the inner right eye. Eye movement data is related to stagesof sleep such as rapid eye movement REM, which indicates a deep sleepstate and dreaming.

[0040] Zone 52 is designated for an EOG to detect electrical eyemovement signals for the outer left eye and zone 62 is designated forelectrical eye movement signals for the outer right eye.

[0041] Zone 53 is designated for electro-myography (EMG) to detectelectrical signals from muscle contractions in the upper left chin. Zone63 is correspondingly for the upper right chin. Zones 54 and 64 are forthe lower left and lower right chin respectively. The amplitude of thechin signals is proportional to the relaxation state and subsequentsleep state of the patient.

[0042] Zone 55 is the EMG for the upper left lip, giving informationabout sleep stages. It is proportional to the relaxation and sleepstates of the patient. Zone 65 is the EMG for the upper right lip.

[0043] Zone 56 is the EMG for the left nasal inner mask it also providessignals for the lip movements and is proportional to the relaxation andsleep states of the patient. Similarly zone 66 is for the right nasalinner mask EMG.

[0044] Zones 57 and 67 are for the oral left and oral right outer maskEMG signals which are also proportional to the relaxation and sleepstates of the patient.

[0045] Zone 70 is for pressure sensor ports for airflow determination.

[0046] Microphone 80 on the mask detects the patient's breathing orsnoring sounds.

[0047]FIG. 6 shows an alternate embodiment where two sensors 58 and 68are used to find the patient's electrocardiogram ECG. This data is alsouseful for monitoring a patient. The patient's heart functions provide alot of useful data about the patient's condition. Pulse Transit Time(PTT) is the time it takes ECG pulses to travel from the heart to asensor such as a sensor placed on the head, on a finger tip, or on theear. PTT sensors can be in the mask, on sensors connected to the mask,or sensors used in conjunction with the mask. PTT measurements are usedto determine patient arousal and qualitative blood pressure variation.

[0048] Thermal sensor 81 is used on the inside surface of the mask todetect nasal breathing. Thermal sensor 82 is used on the outside surfaceof the mask to detect oral breathing. The thermal sensitivity of thesensors 81 and 82 on the surface of the mask 10 opposite the nose ormouth indicates if the patient is breathing through his nose or mouth.The thermal sensors 81, 82 may alternatively be placed on the inside ofthe mask 10, on the outside of the mask 10, or inside of the material ofmask 10 for detecting breathing. The thermal sensors 81, 82 may be athermistor material, a thermocouple material or any other temperaturesensitive material. The thermal sensors 81, 82 may be coatings on theinside of the mask, the outside of the mask or in the mask. The thermalsensors 81, 82 detect heat, which is proportional to the amount ofbreathing.

[0049] It is important to detect oral breathing for undetected orpartially undetected oral breathing effects the integrity of the patientbreathing gas breath monitoring and subsequently compromises the idealgas delivery to the patient. It is important to detect mouth breathingto assist in diagnosis of sleep disordered breathing. Further, controlof a mask nasal ventilation is effected by mouth breathing.

[0050] A pressure sensor 84 measures the pressure inside of the mask toindicate if there is positive pressure inside the mask. A pressure dropmay indicate a leak.

[0051] A surface reflective oximetry sensor 85 on the inside of the maskdetects the patient's pulse rate and oxygen saturation.

[0052] A surface blood pressure sensor 90 on the perimeter 12 of themask 10 in contact with the patient can be used to monitor the patient'sblood pressure.

[0053] A thermistor 91 on the perimeter 12 of the mask 10 in contactwith the patient can be used to monitor the patient's temperature.

[0054] A patient recycled air detection system having a sensor 95 on theinside surface of the mask detects the amount expired air from thepatient remaining in the mask 10. High levels of expired gas in the maskindicates the mask is not being flushed out and may lead to problems ifnot enough fresh gas is introduced.

[0055] A patient back gas occurrence detector 97 in the mask hoseconnector 14 detects the amount of expired gas in the mask returningwith newly delivered gas.

[0056]FIG. 7 shows thermal sensors 83 such as thermistors orthermocouples on the inside or outside of the mask adjacent theperimeter 12. These sensors can be attached to a thermally conductivematerial 92 around the perimeter of the mask 10. Alternatively thethermally conductive material may be on portions of the perimeter. Thisthermally sensitive material can be on the inside surface of mask 10,the outside surface of mask 10 or embedded within the mask material.Detection of a temperature change by thermal sensors 83 or thermalsensors 83 on thermally conductive material 92 correlates with maskleakage around the perimeter. The thermally sensitive material may be athermally sensitive material in the mask on the inside of the mask, onthe outside of the mask or on the perimeter of the mask. The thermallysensitive material may be a thermistor, a thermocouple, or any otherthermally sensitive material.

[0057] Gases leaking from the mask 10 will cause a temperature changeassociated with the thermally conductive material 92 and sensors 83 andallow a healthcare specialist real-time monitoring of leak status orpost monitoring status of mask leakage. In some instances this can belife saving where a patient's gas delivery is critical and in othercases the leakage incidence can assist in the diagnosis of a patient.This assistance may be in the form of alerting a health care specialistthat the gas delivery was subject to leakage and this may affect patienttreatment and patient diagnostic conditions. In other instances the gasleakage detection can allow the gas delivery system to automaticallycompensate for the gas leakage.

[0058] A light sensitive resistor 86 on the outside surface of the mask10 indicates the ambient lighting conditions of the patient.

[0059] Position sensors 87 indicate position or activity of the patient.For example these sensors show if the patient is lying down and ismotionless. Such a sensor may be a moving ball across switch contacts,or mercury sensor switches.

[0060] Body movement sensor 88 can be a PVD or piezo material or micromechanical to detect the patient's body movements extent and rate todetermine a wake versus rest state.

[0061] All of the above sensors may send data by telemetry rather thanby cable 30.

[0062] All of the above collected data may be used to monitor a patientfor a variety of uses including sleep studies, anesthesia and sleepapnea.

[0063] The data collected can be converted to a serial data stream toallow a single wire to interface all the sensors. The sensors mayprovide data to adjust gas delivery to the patient.

[0064] Gain and filtering adjustments to the signals may be used tocondition the signals close to source for optimal noise and signalperformance.

[0065] An electrical bias to sensors such as a patient position sensors,thermal conductive zones, microphones, or light dependent resistor maybe applied.

[0066] A computer may process the data or simply store the data to fromthe monitoring sensors in the mask or straps attached thereto. Themonitoring data may be used to diagnose a patient, provide feedback tomachines attached to the patient, increase or decrease air supplies to apatient or perform other functions.

[0067] The mask 10 may be made such that it is a sterile disposable unitfor medical use thus lowering costs of treatment by not needing tosterilize masks for new patients and providing a more sterile treatmentthan reusable masks.

[0068] In one embodiment, the present invention is utilized to controlthe delivery of a gas to a patient. An example of EEG data controllingin a bio-feedback application the delivery of gas to a patient may bewhen a patient has a nasal ventilation device such as a ventilatorContinuous Positive Air Pressure (CPAP), Bi-Positive Air Pressure(BPAP), Variable Positive Air Pressure (VPAP), Sleep Linked Positive AirPressure (SPAP) and the EEG electrodes provide one of the vital signs ofif the patient is asleep. Gas is only applied to the mask when thepatient is deemed to be asleep. The sensors in the mask 10 are betterable to determine when the patient is actually asleep before applyingassisted nasal ventilation. Premature application of pressure canprevent the patient from sleeping due to the added discomfort ofpositive pressure. This function is more sophisticated, sensitive topatient comfort than delay ramp systems commonly used on someventilation systems.

[0069] Ventilation devices that use delay ramps do not take into accountthe patient's sleep state, and so these units are not able to adjust theapplication of gas to stages of deeper sleep when they are moretolerable to a patient. Furthermore, these units are also not able toadjust the applied pressure to levels which are better tolerated by thepatient.

[0070] As such, the inclusion of a bio feedback mechanism in thedelivery of gas significant advantages. As shown in FIGS. 8, 9, and 10,in another embodiment, the present invention is adapted to providebio-feedback that is utilized to control a gas delivery device. Theembodiment is generally comprised of a mask assembly 100 having a body101 and a forehead support 102 extending from the body. The body iscomprised of an internal surface 104, an external surface 106, and aperimeter surface 108. The forehead support 102 extends upwardly fromthe body and is sized and shaped to contact a patient's forehead. Theforehead support 102 includes a forehead support bar 103 adapted tocontact a patient's forehead.

[0071] As shown in FIGS. 11 and 12, in one embodiment, the body 101includes wings 110 extending from the external surface 106. The wings110 include an attachment surface 109 serving as a point of attachmentto mask straps 111. Conductive carbonized silicon rubber padding 113 arepositioned along the strap to detect EEG signals. The external surface106 also includes a sensor seat 112 wherein a thermistor 114 isdetachably connected.

[0072] In one embodiment, the perimeter surface 108 has cushioning 115extending therefrom. The cushioning 115 is preferably made a siliconplastic material and is sized and shaped to form an effective sealaround a patient's nose. It is also contemplated of shaping the mask toconform to the entire nasal and oral region like general breathingmasks. A thermistor coating 116 is placed on the cushioning in order todetect temperature gradient differences indicative of a leak in themask. The cushioning 115 may also include conductive surfaces 117 todetect physiological signals such as ECG signals. The cushioning 115provides a comfortable seal around a patient's nose, while reducing thepossibility of creating facial sores generally attributed to themetallic sensors used in the prior art.

[0073] As shown in FIGS. 8, 9, and 11, in one embodiment, the foreheadsupport 102 includes a forehead support bar 103 which extends generallyperpendicular to the rest of the forehead support 102. The foreheadsupport bar 103 acts to stabilize the mask 100 on the patient's face andto position sensors along the patient's forehead. A pulse oximetrysensor 118 and EEG sensors 120 are connected to the forehead support bar103. The forehead support 102 also includes a channel 119 wherein leadsfrom the various sensors travel through.

[0074] In one embodiment, the EEG sensors 120 includes a conductivecarbonized silicone rubber padding 122 which provides cushioning for theforehead support bar and a conductive surface for detecting EEG waves. Asupport 121 stabilizes contact between a patient's forehead and the EEGsensors 120. The forehead support bar 103 positions the EEG sensors 120on a patient's forehead just below standard electrode placementpositions FP1 used for an EEG channel and FP2 used for a patient ground.The positioning of the EEG sensors on the patients forehead enables themask to take relevant EEG readings.

[0075] One or more oximetry sensors or pulse-wave sensors may bepositioned on the forehead stabilizer pads 103 of the breathing maskutilized, for example, in nasal positive air pressure systems, patientoxygen therapy, or ventilator breathing masks. Electrophysiologicalsensors including (but not limited to) sensors enabling theinvestigation of sleep and breathing-related sleep disorders such aselectromyography (EMG), electroencephalography (EEG), electrooculography(EOG) and electrocardiography (ECG), may be embedded in the foreheadstabilizer pads 103 of a breathing mask, such as a nasal positive airpressure, patient oxygen therapy, or ventilator breathing mask (but notlimited to).

[0076] This capability can enable the monitoring or derivation of pulsetransit time (PTT), PTT-derived arousals, pulse arterial tone (PAT),pulse wave amplitude (PWA), respiratory effort related arousals(RERA)for diagnosis or treatment countermeasure purposes, both inreal-time or post monitoring.

[0077] One or more sensors can be separated with non-conductive barriersbetween each respective sensor to enable a number of appropriatelyplaced sensors to be positioned within the mask forehead stabilizer pads103.

[0078] Electrophysiological sensors including (but not limited to)sensors enabling the investigation of sleep and breathing-related sleepdisorders such as electromyography (EMG), electroencephalography (EEG),electrooculography (EOG) and electrocardiography (ECG), embedded in theface seal of the breathing mask, or embedded as (such as but notsilicon, rubber, plastic or other flexible material), including carbonimpregnated silicon or rubber forming a near perfect seal but containingan effective conductive interface between the breathing mask seal andthe subject's face.

[0079] One or more sensors can be separated with non-conductive barriersbetween each respective sensor to enable a number of appropriatelyplaced sensors to be positioned within the mask seal perimeter. In thisway a means is enabled, for example (but not limited to) for cheek EMGto be detected (with a pair of sensors separated but appropriatelylocated to detect the subjects cheek EMG signal (this signal declines inelectrical activity as a subject transitions into deeper stages orsleep, until the lowest cheek EMG activity during REM sleep), EOG(detectable via conductive zones around the upper nose bridge sectionand near the subjects eyes), EEG (frontal EEG and arousals alsodetectable from nose or top of mask conductive perimeter zone, forexample). Oral breathing detection material including thermallyconductive polymer or material (such as but not silicon, rubber, plasticor other flexible material) impregnated or embedded, or attached toinside or particularly outside surface of breathing mask, enablingdetection of nasal and or oral (via subject's mouth) breathing,respectively. Detection of oral breathing can be very important withnasal gas delivery such as a nasal positive air pressure, patient oxygentherapy, or ventilator breathing mask (but not limited to) due to thefact that if this breathing goes undetected (as in previous art nasalmasks) then the optimal therapy control delivery to the subject iscompromised (the device delivering the gas underestimated the actualbreathing depth or volume of the subject due to the undetected breathing“leakage” via the mouth.

[0080] Mask seal leakage detection can be detected by using thermallyconductive polymer or material ((such as but not silicon, rubber,plastic or other flexible material) impregnated or embedded, or attachedto inside or particularly outside surface of breathing mask face seal.By positioning thermally sensitive material in one or more zones aroundthe face seal it is possible to detect and compute the amount of leakageexperienced by the subject receiving gas delivery therapy. Theinformation derived from such “leakage” enables more accurate andprecise computation of the therapy devices gas delivery requirements tocounter the actual breathing stress, sleep disorders or other healthconditions being treated by the gas deliver system. Detection of maskperimeter leakage can be very important with nasal gas delivery such asa nasal positive air pressure, patient oxygen therapy, or ventilatorbreathing mask (but not limited to) due to the fact that if thisbreathing goes undetected (as in previous art nasal masks) then theoptimal therapy control delivery to the subject is compromised (thedevice delivering the gas underestimated the actual breathing depth orvolume of the subject due to the undetected breathing “leakage” via themouth.

[0081] Patient position sensor-breathing can be highly effected bypatient position (upright, lying on back, left-side, right side, forexample). The integration of a position sensor within the mask can alsoallow transmission of valuable data for improved gas delivery decisionand control.

[0082] Typically, data sampling for the EEG sensor is set to 16 bit and512 samples per second. Preferably, unfiltered EEG data received fromthe EEG sensors 120 are high pass filtered and low pass filtered to 0.15Hz and 200 Hz, respectively.

[0083] As shown in FIG. 12, in one embodiment, EMG electrodes 125 areintegrated on the mask straps 111. The EMG electrodes 125 are comprisedof soft cushions of conductive carbonized silicon rubber. The EMGelectrodes are positioned on the mask straps so that when the mask isapplied to a patient, the EMG sensors are positioned over the massetermuscle (cheek) and A1, for the EMG channel data and the reference,respectively. The positioning of the EMG electrodes with respect to thepatient enables the present invention to monitor muscle activity whichare indicative of sleep disorder breathing and of arousal.

[0084] In one embodiment, the EMG electrodes 125 are data sampled at 512samples per second. The EMG signals are typically high pass and low passfiltered at 70 Hz and 200 Hz, respectively.

[0085] The location of the pulse oximetry sensor 118 on the foreheadsupport bar 103 enables the present invention to take accurate oximetryreadings using a unique reflective oximetry techniques. The pulseoximetry sensor 118 includes an LED light and a light sensor. The LEDbeams light through the forehead skin and to the skull. The lightbounces of the skull and is reflected back to the light sensor which inturn converts the light into an analog signal. The analog signal is thenhigh pass filtered at about 0.01 Hz and is then analyzed using knownpulse oximetric techniques to determine SPO2 levels, a pulseplethysmography waveform, and a heart rate.

[0086] In one embodiment, the subject mask assembly 100 is incommunication with a control system 124 for a gas delivery device. Onesuch control system is described in U.S. Pat. No. 6,397,845 to Burton,the contents of which are hereby incorporated by reference in itsentirety. The control system 124 is adapted to determine a sleep stateof a patient from the physiological signals which are being detected bythe mask assembly 100. The patient's sleep state is then used as adeterminate for controlling the delivery of gas to the patient.

[0087] One of the sleep states detected in U.S. Pat. No. 6,397,845 isthe state of arousal. Arousals usually do not cause a person to wake up,but they often transition a patient away from deeper stages of sleep.Furthermore, arousals are often followed by a relatively long periodbefore reentering deeper stages of sleep such as REM or slow-wave. As aresult, a person who has numerous arousals may experience fragmentedsleep which in turn causes excessive daytime sleepiness or othersymptoms.

[0088] In one embodiment, arousal is determined using Pulse Transit Time(PTT). Studies have shown that sleep disorders such as apnea, hypopneaor upper airway resistance result in an accompanying arousal, and thisarousal is accompanied by changes in heart rate, a transient burst ofsympathetic activity, and a surge in blood pressure. Obstructive sleepapnea can be correlated with an obvious and measurable increase inintrathoracic pressure associated with obstructive effort andcardiobalistogram effect. The cardiobalistogram effect is created whenthe lungs apply pressure to the heart. This compresses the heart andreduces the volume of blood pumped by the heart. These cardiovascularchanges are recognizable by way of a transient but significant dip inthe patient's baseline PTT value.

[0089] PTT is the time taken for the pulse wave to travel between twoarterial sites. The blood pressure is directly proportional to the speedthat the arterial pressure wave travels. A rise in blood pressurerelates to faster pulse wave and thus shorter PTT. Conversely, a drop inblood pressure results in a slowing of the pulse wave and an increase inPTT.

[0090] In one embodiment, PTT is obtained directly by utilizing sensorslocated on the present invention. A detector receives input from themask and generates a plethysmography waveform. A second detectorreceives input from the mask and generates an ECG signal. The waveformand the signal are inputted into the controller and a PTT reading iscalculated.

[0091] The PTT is derived by utilizing a plethysmography waveformobtained by using pulse oximetry readings obtained from the pulseoximetry sensor 118 in combination with an ECG signal detected along theperimeter surface 108. The ECG R or Q wave can be used as the startpoint for the PTT measurement and the end point of the PTT measurementcan be the point representing 25% or 50% of the height of the maximumpulse wave value from the pulse oximetry sensor 118.

[0092] The control system 124 can also be utilized to control deliveryof medications and anesthetic agents to a patient. In such aconfiguration, the control system is typically in communication with adrug dispensing apparatus such as an infusion pump.

[0093] The matter set forth in the foregoing description andaccompanying drawings is offered by way of illustration only and not asa limitation. While a particular embodiment has been shown anddescribed, it will be obvious to those skilled in the art that changesand modifications may be made without departing from the broader aspectsof applicants' contribution. The actual scope of the protection soughtis intended to be defined in the following claims when viewed in theirproper perspective based on the prior art.

1. A mask assembly comprising: a body having an internal surface, anexternal surface, and a perimeter surface; and a forehead supportconnected to the body, the forehead support having an EEG sensor locatedthereon.
 2. The assembly of claim 1, wherein the perimeter surfaceincludes a padding material having a thermosensitive coating.
 3. Theassembly of claim 1 wherein the forehead support includes a foreheadsupport bar extending in a generally lateral direction from the foreheadsupport bar.
 4. The assembly of claim 3, and wherein an SPO2 sensor islocated on the forehead support bar.
 5. The assembly of claim 4, whereinthe EEG sensor includes a pad comprised of a conductive carbonizedrubber material.
 6. The assembly of claim 1, and further comprising astrap extending from the mask, and wherein a physiological sensor islocated on the strap.
 7. The assembly of claim 1, wherein a portion ofthe conductive padding is adapted to measure EOG.
 8. A gas deliverysystem comprising: a mask having at least one physiological sensorconnected thereto; a gas delivery device having an adjustable gasdelivery setting; and a processor in communication with the gas deliverydevice and the sensor, the processor adapted to determine the existenceof a sleep disorder and to adjust the gas delivery setting basedthereon.
 9. The system of claim 8, wherein the sensor is an EMG sensor.10. The system of claim 8, wherein the sensor is an ECG sensor.
 11. Thesystem of claim 10, and further comprising a SPO2 sensor connected tothe mask.
 12. The system of claim 8, wherein the sensor is an EEGsensor.
 13. The system of claim 8, wherein the processor is also adaptedto determine patient arousal.
 14. A gas delivery system comprising: amask having at least one EEG sensor connected thereto; a gas deliverydevice having an adjustable gas delivery setting; and a processor incommunication with the gas delivery device and the EEG sensor, theprocessor adapted to determine arousal and to adjust the gas deliverysetting based thereon.
 15. The system of claim 14, wherein an SPO2sensor and an ECG sensor are connected to the mask, and wherein theprocessor is in communication with both sensors and is adapted to derivea PTT value from an output of each sensor.
 16. The system of claim 14,and further comprising a strap extending from the mask and a pluralityof EMG sensors located on the mask and strap, the EMG sensors positionedto detect muscle activity related to sleep state.
 17. A method ofdelivering gas comprising: providing a mask adapted to detectphysiological signals and to deliver a gas; providing a gas deliverydevice in fluid communication with the mask and having an adjustable gasoutput; determining a sleep state from physiological signals detected bythe mask; and adjusting the output from the gas delivery device based onthe sleep state.
 18. The method of claim 17, wherein determining a sleepstate includes determining arousal.
 19. The method of claim 18, whereindetermining arousal includes calculating PTT values from an SPO2 and ECGreadings.
 20. The method of claim 18, wherein determining arousalincludes analyzing cortical and subcortical EEG signals.
 21. A method ofobtaining SPO2 reading from a mask comprising: attaching a light sourceand a light sensor on a mask so that the light source and light sensorare positioned to contact a person's forehead; illuminating the lightsource; detecting light from the light source as it deflects from theperson's skull; and converting the detected light into an analog signal.22. The method of claim 21, and further comprising the additional stepof high pass filtering the analog signal.
 22. A method of detecting oralor nasal breathing during nasal ventilation, the method comprising:providing a mask adapted to form a seal between a patient's nose andmouth, the mask having an interior surface and an exterior surface, themask also having a first thermal sensor on the interior surface and asecond thermal sensor located on the exterior surface to be adjacent thepatient's mouth; detecting a temperature change in the first or secondthermal sensor.
 23. An apparatus comprising: a mask having a bodyposition sensor attached thereto; a processor in communication with thesensor and adapted to a determine body position from the body positionsensor's output.
 24. The apparatus of claim 23, and further comprisingmovement sensor attached to the mask and in communication with theprocessor, and wherein the processor is also adapted to determinemovement from an output of the movement sensor.
 25. A method ofdetecting a leak in a breathing mask: providing a mask having aperimeter surface with a plurality of thermally conductive surfacesdistributed throughout the perimeter surface; and detecting atemperature change in any of the plurality of thermally conductivesurfaces.
 26. A mask assembly comprising: a body having an internalsurface, an external surface, and a perimeter surface; and a foreheadsupport extending from the body and adapted to contact a foreheadsurface of a patient during use, the forehead support having a pluralityof sensors located thereon for detecting electrophysiological signals ofthe patient.
 27. The mask assembly of claim 26 wherein the foreheadsupport includes a support pad in contact with the forehead surface. 28.The mask assembly of claim 26 further comprising: a movement sensor fordetecting movement of the patient during use.
 29. The mask assembly ofclaim 26 further comprising: a mask seal leakage detector.
 30. A gasdelivery system comprising: a gas mask adapted to fit on a patient; agas delivery device having an adjustable gas delivery; and a processorin communication with the gas delivery device and a cardiac pacemaker,the processor adapted to adjust the gas delivery based on a signal fromthe cardiac pacemaker.
 31. The gas delivery system of claim 30 whereinthe processor receives an additional electrophysiological signal fromthe patient, and said processor determines the existence of a sleepdisorder based upon the signals.